1. Field of the Invention
The present invention relates to a process for manufacturing a friction plate for a clutch, and an apparatus for use in the process.
2. Description of the Prior Art
In manufacturing a friction plate for a clutch, a procedure has been conventionally employed which comprises subjecting a sheet of a friction article to a cutting operation to provide a predetermined sized cut, subjecting the cut to a punching to provide an annular friction article, adhering the annular friction article to an annular core, and subjecting the annular friction article to a machining or to a shaping with a metal mold to provide a large number of radially extending oil grooves on the annular article.
However, if a punching is employed, there is encountered a problem that the yield rate of the friction article is as low as 20 to 40%, resulting in an inferior economy.
When the oil grooves are made by machining, the depth of the groove tends to become shallow in order to avoid a damage to the core. As a result, oil fails to drain in practice, bringing about a reduction in durability due to degradation in cooling performance, a generation of a dragging noise, a lowering in operation feeling and the like. When the oil groove is made by shaping, a mold for each of friction plates having different sizes must be provided, which is extremely uneconomical.